A retired senior police officer jailed for striking a bystander with a baton during Hong Kong’s 2014 pro-democracy Occupy protests complained in appeal on Wednesday that his trial had been a circus.

Lawyers for Frankly Chu gave 28 reasons why his victim was not a credible witness after revealing a new piece of footage unearthed from some 2,800 online videos capturing what has become one of the most controversial scenes of policing during the civil disobedience movement.

Charlotte Draycott SC also complained that Principal Magistrate Bina Chainrai was unfair to her client when she “refused to look at the wider picture to see what took place and focused on the seconds of the blow” that left Osman Cheng Chung-hang with a “trivial” injury.

“We must take a step back and look critically at the evidence,” Draycott told the High Court. “The trial was a circus. There was endless interruption and confusion. The public gallery was packed. Emotions ran high … When the magistrate came to deal with the evidence, she did not analyse the evidence, she simply said, ‘I believe in [Cheng]’.”

Chu, 58, was jailed for three months in January for striking Cheng, 28, with a baton during a clearance operation in Mong Kok on November 26, 2014. Cheng had testified that the blow injured the right part of his neck.

The offence of assault occasioning actual bodily harm is punishable by up to three years’ imprisonment.

The former superintendent is appealing against both his conviction and sentence before Mr Justice Albert Wong Sung-hau.

The case was the second time that a court had found officers guilty of using excessive force while policing the 79-day Occupy protests, which shut down major roads as protesters called for greater democracy. In February last year, seven police officers were jailed for two years on the same charge for punching and kicking an activist who poured liquid over their colleagues. Their appeal will be heard in November.

On Wednesday, more than a hundred people filled the courtroom’s antechamber to the brim to watch a live telecast of the two-day appeal hearing, while some of Chu’s supporters waited outside the building, where a large blue billboard with his portrait had been erected. “I support [Frankly Chu],” it read.

Draycott argued that her new video put things in better context as it showed the dynamic situation Chu was faced with and undermined Cheng’s testimony, which she complained Chainrai had accepted in “absolute belief” without critical examination.

Footage played in court showed Cheng standing still and mouthing something to officers when others around him followed police instructions to leave.

Cheng testified that he was telling officers he only passed by the scene, while Chu explained that he had made a split-second decision to strike Cheng after seeing him display an aggressive act towards a colleague when officers were clearing the pavement to prevent a reoccupation.

“If he thought that, the blow was justified,” his counsel argued. “It’s not something he wanted to do, it’s something he thought he needed to do. That’s a fine judgment which the magistrate didn’t tackle.”

As a result, Draycott said Chainrai had failed to consider the events from her client’s perspective to analyse if he actually intended to do something unlawful.

Draycott said her client had correctly identified Cheng as an active participant since his Instagram and testimony in court revealed he was present in previous clearance operations and spent half of the 79 days in the Admiralty occupation site.

“He was not just a passer-by,” she continued. “He was challenging the police.”

She also accused Cheng of lying about his injuries when he claimed he was assaulted in the shin by another officer that evening as she drew the court’s attention to an Instagram post that pictured an injury to the same body part sustained in the previous night.

But prosecutor Daniel Marash SC countered the video would not help Chu’s case since Chainrai was fully aware of the events leading up to the blow, given his extensive testimony at trial.

The prosecution’s full reply will be heard on Thursday, before Wong decides whether to admit the new video into evidence.